Isaac approaching hurricane strength

By: Angela Fritz , 9:14 PM GMT on August 27, 2012

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Isaac is walking the line of hurricane status this afternoon after a hurricane hunter mission investigated the storm and found winds of 80+ mph with the SFMR instrument, which looks down at the surface from the plane and estimates what wind speeds are. This instrument has a notoriously rough time in doing so when there's heavy rain, and since the strongest winds were recorded coinciding with the strongest rain, you can imagine that this region of high wind speed could be suspect. The hurricane hunter mission is still in the storm, so I imagine they will issue a special update if needed. Currently the best estimate of wind speed within the storm is 70 mph. Isaac's pressure has been dropping today as well and is now 981 mb. Isaac is moving northwest at 12 mph--no change since this morning. Satellite loops show that Isaac remains large, though asymmetric, with most of the strong thunderstorm activity on the west and southwest side. Isaac's southeast side continues to struggle with dry air and wind shear, which could help to moderate Isaac's intensity as it approaches the coast.

An oil platform in the northern Gulf of Mexico is reporting sustained winds from the north-northeast at 40 mph this afternoon. A buoy west of Tampa, Florida is recording sustained winds around 30 mph, and platforms south of Louisiana are recording winds from 35-40 mph. The widespread heavy rain of yesterday has lightened up in Florida, but a strong line of thunderstorms in one of Isaac's outer bands is training northward along and offshore of the east coast of Florida, affecting everyone from Miami to Jacksonville.

This afternoon the AP reported that Isaac's death toll in Haiti jumped to 19, which puts Isaac's total death count at 21. It appears most of the deaths in Haiti were due to collapsing structures.


Figure 1. Satellite imagery of Tropical Storm Isaac around 3pm EDT on Monday.

Track forecast:
Models seem to be coming into better agreement today on where Isaac will make landfall, closing in on Louisiana and New Orleans as most likely landfall point. The ECMWF, HWRF, and UKMET all suggest New Orleans as the landfall location. The GFS is only slightly west of that. The GFDL is the farthest west, predicting landfall near the Louisiana-Texas border. Landfall timing remains Tuesday night. Beyond landfall, Isaac is expected to move north toward the Midwest through the rest of this week, however, models are showing that the system will likely slow down around landfall time, prolonging impacts like surge and inland flooding.

Intensity forecast:
The closer Isaac gets to landfall without having formed an eye, the better it is for intensity at landfall. Isaac has strengthened only modestly in the past 24 hours, and is still struggling with a less-than-conducive atmospheric environment. The HWRF remains on the high end of the intensity spectrum, suggesting Isaac will be a weak category 2 upon landfall. Other models suggest it will be a strong category 1, but the difference is splitting hairs. The National Hurricane Center's official forecast is for Isaac to continue strengthening over the next day, reaching category 2 at landfall.


Figure 2. Tide gauge data from St. Petersburg, Florida. The green line shows the storm surge. As Isaac's counterclockwise winds blew offshore this morning, water levels feel two feet at St. Petersburg. The winds switched to onshore this afternoon as the center of Isaac moved more to the northwest, bringing a storm surge of two feet to the city.

Storm surge observations from Isaac
This morning, as Isaac's counter-clockwise winds brought offshore winds to the Tampa/St. Petersburg area, ocean waters fell two feet along the coast. This afternoon, winds have shifted to blow onshore, and a two foot storm surge has been observed at Naples, Fort Meyers, and St. Petersburg on the west coast of Florida. Water levels have also begun to rise along the coast of Louisiana, with a storm surge of 1.5 feet already occurring at Shell Beach on the east side of New Orleans in Lake Borgne.

Angela and Jeff

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Quoting scott39:
Isaac is going to put a show on tonight.


I just hope he's not trying to do an Andrew impersonation.
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Quoting CaneHunter031472:
Gosh 9 to 11 feet surge where I live. Mandatory evacuation as of tomorrow. I guess it is what it is. I really thought I dodged this one.


Where do you live?
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NRT, what's the NOAA2 aircraft doing?


000
URNT15 KWBC 272121
NOAA2 2809A ISAAC HDOB 11 20120827
211130 2714N 08537W 7518 02469 9957 +173 +102 120045 046 036 001 00
211200 2713N 08539W 7518 02468 9956 +173 +103 115044 044 036 002 00
211230 2712N 08540W 7515 02469 9960 +166 +103 115046 046 037 001 00
211300 2710N 08541W 7519 02466 9954 +172 +106 117046 046 037 001 00
211330 2708N 08543W 7519 02464 9947 +178 +104 116048 048 039 003 00
211400 2706N 08544W 7519 02464 9948 +176 +102 112048 048 040 002 00
211430 2705N 08545W 7517 02461 9947 +173 +100 112047 047 039 002 00
211500 2703N 08546W 7520 02458 9948 +170 +108 111046 047 040 003 00
211530 2701N 08547W 7517 02458 9945 +169 +118 115047 047 042 005 00
211600 2659N 08548W 7518 02456 9948 +161 +126 110047 049 042 005 00
211630 2658N 08549W 7515 02455 9941 +167 +122 113047 048 042 005 00
211700 2656N 08550W 7519 02447 9938 +167 +115 112050 051 045 004 00
211730 2654N 08551W 7517 02445 9936 +164 +124 118051 052 045 004 00
211800 2652N 08553W 7518 02441 9937 +158 +134 120049 051 044 005 00
211830 2651N 08554W 7517 02439 9934 +155 +141 121047 048 046 004 00
211900 2649N 08555W 7517 02436 9928 +156 +149 124049 050 046 005 00
211930 2647N 08556W 7517 02432 9926 +155 +146 126050 050 048 003 00
212000 2646N 08557W 7519 02428 9923 +157 +136 126048 049 048 003 00
212030 2644N 08558W 7517 02427 9915 +162 +141 126049 049 047 004 00
212100 2642N 08559W 7520 02422 9907 +167 +148 125047 050 048 003 00
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Hey, Isaac for me is Hurricane!!!
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Quoting noraneinsite:
Still struggling with dry air. Will it mix out the dry air and really ramp up before lanfall?


It probably could because of its large size.
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27/1745 UTC 26.4N 86.0W T4.0/4.0 ISAAC -- Atlantic
Member Since: May 21, 2006 Posts: 5091 Comments: 115256
96. CJ5
Quoting angelafritz:
Has anyone else noticed that I struggle most with simple figures of speech? First, it was the elbow of Florida. Now it's pulling hairs. :)


You have been doing a great job! I look forward to seeing you post more.
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Isaac is going to put a show on tonight.
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Dry air?

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Classic comma shap, just inverted.

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Quoting weatherh98:


Hey man, just do me one favor

Don't flood my house.

I'll try not to but no promises. Lots of rain will be dumped and there will be a good amount of storm surge.
Member Since: March 16, 2012 Posts: 127 Comments: 7948
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Kermit finding 990mb at the edge of the CDO
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Still struggling with dry air. Will it mix out the dry air and really ramp up before lanfall?
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Quoting Stormbugn:
I am about 50 miles inland from Gulfport, MS and I think we are feeling the first winds (very light) from the storm. Is that even possible????
LOCATION...26.4N 86.2W
ABOUT 320 MI...515 KM SSE OF MOBILE ALABAMA
ABOUT 255 MI...415 KM SE OF THE MOUTH OF THE MISSISSIPPI RIVER
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...981 MB...28.97 INCHES


TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM
FROM THE CENTER.
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Quoting TheHurricaneDundee:

I don't know what they ment by at TWC when they said it was wrapping some dry air into it. it looks fine to me


See that blue swirl wrapping into the north side of the main convection surrounding the COC? Dry air.
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Quoting FrancesJeanne:
Do any of you Treasure Coast folks know how bad the flooding is in the White City area? My daughter is waiting for me to pick her up at a friend's house on Sunrise just north of Midway, but I'm not sure whether I should attempt to get there or just let her spend the night.


It was pretty bad when I crossed midway on 25th at @ 2:30 but I here it has receded a little bit now. White city park is notorious for bad flooding so it is probably still pretty bad.
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Quoting taco2me61:
I could not beleive they called Mobile Bay in MS.... OMG this guy is on Weatherunderground but was in Mobile Bay MS and showing the USS Alabama....
Come on folks at least get the city Right :o)

Taco :o)




Taco r u for real. what the TWC has people here already or something?

sheri
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Quoting FrancesJeanne:

Ugh. That's what I figured. Thanks :)


I say let her spend the night with her friend ...both of you need to stay safe
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Quoting wxchaser97:

I'm winking at myself then;) Anyway Isaac is looking better at this hour.


Hey man, just do me one favor

Don't flood my house.
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Quoting CaneHunter031472:
Gosh 9 to 11 feet surge where I live. Mandatory evacuation as of tomorrow. I guess it is what it is. I really thought I dodged this one.


Be careful and stay safe
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I am about 50 miles inland from Gulfport, MS and I think we are feeling the first winds (very light) from the storm. Is that even possible????
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Quoting WeatherNerdPR:
Good Afternoon.
981mb TS? lol Isaac is weird.
He seems to be showing off some sort of eye feature.
He looks like a 8 week old fetus.
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Quoting WeatherNerdPR:
Good Afternoon.
981mb TS? lol Isaac is weird.
He seems to be showing off some sort of eye feature.


Definitely strengthening as we speak.
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Quoting coondini:

So could all of AR, MO, IL, west TN & KY, IN, etc.
Yep

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Good Afternoon.
981mb TS? lol Isaac is weird.
He seems to be showing off some sort of eye feature.
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Eye is just about closed, with the new popcorn on the W side... wow I just can't go to bed because of the beauty (terrifying beauty) of the rapidscan loop..

rapidscan image of isaac
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Quoting coondini:

So could all of AR, MO, IL, west TN, IN, etc.


Wish Jacksonville could have given y'all some rain this year. at 44.05" year to date, we are about 13" above average for the year.
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Quoting CaneHunter031472:
Gosh 9 to 11 feet surge where I live. Mandatory evacuation as of tomorrow. I guess it is what it is. I really thought I dodged this one.


Where from Cane?
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Quoting TomballTXPride:

Not you. Isaac's winking at you.

I'm winking at myself then;) Anyway Isaac is looking better at this hour.
Member Since: March 16, 2012 Posts: 127 Comments: 7948
Quoting GTcooliebai:
Mainland Georgia and parts of Alabama sure could use the rain.

Absolutely. They should get a decent amount, but not enough to remedy the drought completely.
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Gosh 9 to 11 feet surge where I live. Mandatory evacuation as of tomorrow. I guess it is what it is. I really thought I dodged this one.
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Quoting GTcooliebai:
Mainland Georgia and parts of Alabama sure could use the rain.


So could all of AR, MO, IL, west TN & KY, IN, etc.
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Isaac kind of has like a Southern Hemisphere storm appearance to him.
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Quoting hahaguy:


Well I just saw that White City had 9-11 inches of rain so I'd bet it's decently flooded.

Ugh. That's what I figured. Thanks :)
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I said this on the other Blog but I got a little up set because they were talking to someone from Weatherunderground at TWC and they said Mobile Bay MS and showing The USS Alabama in Mobile AL.... OMG please get it right is all I ask.... LOL

Taco :o)
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You are doing fine Angela....great job. Don't worry about the little things like that...you and Dr. Jeff have your hands full. We really appreciate all that ya'll do!
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Won't be to long before TWC officially takes over...
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Chillig.. expecting a 980 or 979 reading :)
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Quoting hydrus:
Thank you Angela..Pretty cool seeing the Doc on TWC. I suspected this would occur, just not so soon..:)..Inland flooding will be a problem with Isaac..
Mainland Georgia and parts of Alabama sure could use the rain.

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58. auburn (Mod)
Quoting angelafritz:
Has anyone else noticed that I struggle most with simple figures of speech? First, it was the elbow of Florida. Now it's pulling hairs. :)


We are lucky to have you!
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It may be an optical illusion but the last few frames of the animated sat image make it look like the clouds in the area of the would-be eye are sinking. Possibly about to clear out?
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Quoting FrancesJeanne:
Do any of you Treasure Coast folks know how bad the flooding is in the White City area? My daughter is waiting for me to pick her up at a friend's house on Sunrise just north of Midway, but I'm not sure whether I should attempt to get there or just let her spend the night.


Well I just saw that White City had 9-11 inches of rain so I'd bet it's decently flooded.
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Quoting MahFL:


So far I have .47 inch here in Orange Park, FL.


I'm in Central Jax, a bit east of Everbank Field.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.